Rf Based Advertisment System

8/8/2019 Rf Based Advertisment System

1/33

CHAPTER 1

INTRODUCTION

Radio Frequency (RF) and wireless have been around for over a century with

Alexander Popov and Sir Oliver Lodge laying the groundwork for Guglielmo Marconis

wireless radio developments in the early 20th century. In December 1901, Marconi

performed his most prominent experiment, where he successfully transmitted Morse code

from Cornwall, England, to St Johns, Canada.

1.1 What is RF?

RF itself has become synonymous with wireless and high-frequency signals,

describing anything from AM radio between 535 kHz and 1605 kHz to computer local

area networks (LANs) at 2.4 GHz. However, RF has traditionally defined frequencies

from a few kHz to roughly 1 GHz. If one considers microwave frequencies as RF, this

range extends to 300 GHz. The following two tables outline the various nomenclatures for

the frequency bands.

Table 1 shows a relationship between frequency (f) and wavelength (). A wave or

sinusoid can be completely described by either its frequency or its wavelength. They are

inversely proportional to each other and related to the speed of light through a particular

medium. The relationship in a vacuum is shown in the following equation:

[BALAKRISHNA ALLU]Page 1


2/33

where c is the speed of light. As frequency increases, wavelength decreases. For

reference, a 1 GHz wave has a wavelength of roughly 1 foot, and a 100 MHz wave has a

wavelength of roughly 10 feet.

Table 2: Microwave Letter Band Designations

1.2 ABOUT PROJECT

The above project on wireless Electronic notice board used in organization,

industries, Bus stations ,railway stations and parks etc . The working of the project is as

follows:

In this project is divided into two sections one is transmitter part and another is

receiver part .In transmitter part whenever we are pressing keys on the keypad, those keys

will be detected by microcontroller. The detected keys will be transmitted through

Wireless STT 433 MHz RF transmitter.

In the receiver section the receiver(STR 433Mhz ) will receive the information and

give it to microcontroller. From there the data was given to Display section. Here display

section is the LCD

This project is used to communicate or transmit a text message from one place toanother place through wireless. The keys will be pressed by using keypad, Those keys

will be decoded by using the Microcontroller and the keys were transmitted through

wireless. At the receiver end the signal was received by the receiver ,the received

message was displayed over the LCD display.



3/33

1.3 BLOCK DIAGRAM

The figure 1.4 shows the RF BASED ADVERTISEMENT SYSTEMblock

diagram. The system is divided into two parts.

1) Transmitter

2) Receiver

Transmitter part consists of Keyboard, microcontroller, MAX3232 and RF transmitter.

1. Micro controller

2. STR 433 MHz

3. HT640 encoder

4. Keypad

Receiver part consists of microcontroller, MAX3232, RF Receiver and LCD.

1. Micro controller

2. STR 433 Mhz RF Receiver

3. HT 648L decoder

4. LCD



4/33



5/33

CHAPTER 2

SYSTEM DESIGN AND OVER VIEW

2.1 VARIOUS COMPONENTS USED IN THE PROJECT

2.1.1 MICROCONTROLLER 89C51

INTRODUCTION:

In 1981, Intel Corporation introduced an 8-bit microcontroller called the 8051.

This microcontroller had 128 bytes of RAM, 4K bytes of on-chip ROM, two timers, one

serial port, and four ports (each 8-bits wide) all on a single chip. At the time it was also

referred to as a system on a chip. The 8051 is an 8-bit processor, meaning that the CPUcan work on only 8 bits of data at a time. Data larger than 8 bits has to be broken into 8-bit

pieces to be processed by the CPU. The 8051 have a total of four I/O ports each 8 bits

wide. Although the 8051 can have a maximum of 64K bytes of on-chip ROM, many

manufacturers have put only 4K bytes on the chip. This will be discussed in more detail

later.

The 8051 became widely popular after Intel allowed other manufacturers to make

and market any flavor of the 8051 they please with the condition that they remain code-

compatible with the 8051. This has led to many versions of the 8051 with different speeds

and amounts of on-chip ROM marketed by more than half a dozen manufacturers. Next

we review some of them. It is important to note that although there are different flavors of

the 8051 in terms of speed and amount of on-chip ROM, they are all compatible with the

original 8051 as far as the instructions are concerned. This means that if you write your

program for one, it will run on any one of them regardless of the manufacture.

Microcontroller is the heart of the system. All the devices connected in the diagram

controlled by the micro controller. Micro controller sends pulses to all the devices, which

are connected with the controller.

We can program it in any language i.e., in assembly or C or C++, it depends upon

the user. In this flash memory is more comparatively with others. In our design, this

controller is compatible and also reliable one.



6/33

Features of the 8051

Feature Quantity

ROM 4K bytes

RAM 128 byesTimer 2

I/O pins 32

Serial port 1

Interrupt sources 6

The 8051 is the original member of the 8051 family. Intel refers to it as MCS-51.

the main features of the 8051.


INTERRUPT

CONTROL

EXTERNAL

INTERRUPTS

CPU

ON-CHIP

ROMFor

ProgramCode

INTERRUPT

CONTROL

ETC

TIMER 0

TIMER 1

OSCBUS

CONTROL4 I/O

PORTSSERIALPORTS

COUNTER

I NPUTS

TED RXD

P0 P1 P2 P3

ADDRESS/DATA

Inside the 8051 Micro controller Block Diagram


7/33

MICROCONTROLLER VERSUS GENERAL-PURPOSE MICROPROCESSOR

What is the difference between a microprocessor? By microprocessor is

meant the general-purpose microprocessors such as Intels x86 family (8086, 80286,

80386, 80486, and the Pentium) or Motorolas 680 x 0 family (68000, 68010, 68020,

68030, 68040, etc.). These microprocessors contain no RAM, no ROM, and no I/O ports

on the chip itself. For this reason, they are commonly referred to as general-purpose

microprocessors.

Microprocessor System Contrasted With Micro controller System

A system designer using a general-purpose microprocessor such as the

Pentium or the 68040 must add RAM, ROM I/O ports, and timers externally to make them

functional. Although the addition of external RAM, ROM, and I/O ports makes these

systems bulkier and much more expensive, they have the advantage of versatility such that

the designer can decide on the amount of RAM, ROM, and I/O. ports needed to fit the task

at hand. This is not the case with micro controllers. A microcontroller has a CPU (amicroprocessor) in addition to a fixed amount of RAM, ROM, I/O ports, and a timer all on

a single chip. In other words, the processor, the RAM, ROM, I/O ports, and timer are all

embedded together on one chip; therefore, the designer cannot add any external memory,

I/O, or timer to it. The fixed amount of on-chip ROM, RAM, and number of I/O ports in

microcontrollers makes them ideal for many applications in which cost and space are

critical. In many applications, for example a TV remote control, there is no need for the

computing power of a 486 or even an 8086 microprocessor. In many applications, the


RAMROM

I/O

Port Timer

Serial

COM

Port

CPU RAM ROM

I/O Timer SerialCOMPort

(b) Microcontroller(a) General-Purpose Microprocessor System

CUP

General-Purpose

Micro-processor

Data bus

Address bus


8/33

space it takes, the power it consumes, and the price per unit are much more critical

considerations than the computing power. These applications most often require some I/O

operations to read signals and turn on and off certain bits. For this reasons some call these

processors IBP, itty-bitty processors .

It is interesting to note that some microcontroller manufacturers have gone as far

as integrating an ADC (analog-to-digital converter) and other peripherals into the

microcontroller.

CHOOSING A MICRO CONTROLLER: -

There are four major 8-bit microcontrollers. They are: Motorolas 6811,

Intels 8051, Zilogs Z8, and PIC 16X from Microchip Technology. Each of the above

microcontrollers has a unique instruction set and register set; therefore, they are not

compatible with each other. Programs written for one will not run on the others. There are

also 16-bit and 32-bit microcontrollers made by various chipmakers. With all these

different microcontrollers, what criteria do designers consider in choosing one? Three

criteria in choosing microcontrollers are as follows: (1) meeting the computing needs of

the task at hand efficiently and cost effectively, (2) availability of software development

tools such as compilers, assemblers, and debuggers, and (3) wide availability and reliable

sources of the microcontroller. Net we elaborate further on each of the above criteria.

CRITERIA FOR CHOOSING A MICROCONTROLLER

1. The first and foremost criterion in choosing a microcontroller is that it must

meet the task at hand efficiently and cost effectively. In analyzing the needs of a

microcontroller-based project, we must first see whether an 8-bit, 16-bit, or 32-bit

microcontroller can best handle the computing needs of the task most effectively. Among

other considerations in this category are:

(a) Speed. What is the highest speed that the microcontroller supports?

(b) Packaging. Does it come in 40-pin DIP (dual inline package) or a QFP (quad

flat package), or some other packaging format? This is important in terms of space,

assembling, and prototyping the end product.

(c) Power consumption. This is especially critical for battery-powered products.

(d) The amount of RAM and ROM on chip.

(e) The number of I/O pins and the timer on the chip.

(f) How easy it is to upgrade to higher performance or lower power-

consumption versions.



9/33

(g) Cost per unit. This is important in terms of the final cost of the product in

which a microcontroller is used. For example, there are microcontrollers that cost 50 cents

per unit when purchased 100, 000 units at a time.

2. The second criterion in choosing a microcontroller is how easy it is to develop

products around it. Key considerations include the availability of an assembler, debugger,

a code-efficient C language compiler, emulator, technical support, and both in-house and

outside expertise. In many cases, third-party vendor (that is, a supplier other than the chip

manufacturer) support for the chip is as good as, if not better than, support from the chip

manufacturer.

3. The third criterion in choosing a microcontroller is its ready availability in

needed quantities both now and in the future. For some designers this is even more

important than the first two criteria. Currently, of the leading 8-bit microcontrollers, the

8051 family has the largest number of diversified (multiple source) suppliers. By supplier

is meant a producer besides the originator of the microcontroller. In the case of the 8051,

which was originated by Intel, several companies also currently produce (or have

produced in the past) the 8051. These companies include: Intel, Atmel, Philips / Signetics,

AMD, Siemens, Matra, and Dallas Semiconductor.

It should be noted that Motorola, Zilog, and Microchip Technology have all

dedicated massive resources to ensure wide and timely availability of their product since

their product is stable, mature, and single sourced. In recent years they also have begun to

sell the ASIC library cell of the microcontroller.

4 kilobytes of ROM is neither too little nor too much.

128 bytes of RAM (SFR registers included) can satisfy the basic needs, but

is not really astounding.

4 ports totaling 32 I/O lines are usually sufficient for connecting to the

environs and are by no means luxury.

Obviously, 8051 configuration is intended to satisfy the needs of programmers

developing the controlling devices and instruments. This is one part of its key to success:

there is nothing missing, yet there is no lavishness; it is meant for the average user. The

other clue can be found in the organization of RAM, Central Processor Unit (CPU), and

ports - all of which maximally utilize the available resources and allow further upgrades.



10/33

PIN DESCRIPTION :

1- 8: Port 1 : Each of these pins can be used as either input or output

according to your needs. Also, pins 1 and 2 (P1.0 and P1.1) have special functions

associated with Timer. 9: Reset Signal : high logical state on this input halts the MCU and clears

all the registers. Bringing this pin back to logical state zero starts the program anew as if

the power had just been turned on. In another words, positive voltage impulse on this pin

resets the MCU. Depending on the device's purpose and environs, this pin is usually

connected to the push-button, reset-upon-start circuit or a brown out reset circuit (covered

in the previous chapter). The image shows one simple circuit for safe reset upon starting

the controller. It is utilized in situations when power fails to reach its optimal voltage. The

reset circuit is as shown in the figure 3.2.1.

Fig 3.2.1: basic reset circuit for the microcontroller.

0-17: Port 3: As with Port 1, each of these pins can be used as universal SS

Pin 10: RXD - serial input for asynchronous communication or serial output for

synchronous communication.

Pin 11: TXD - serial output for asynchronous communication or clock output for

synchronous communication



11/33

Pin 12: INT0 - input for interrupt 0

Pin 13: INT1 - input for interrupt 1

Pin 14: T0 - clock input of counter 0

Pin 15: T1 - clock input of counter 1

Pin 16: WR- signal for writing to external (add-on) RAM memory

Pin 17: RD - signal for reading from external RAM memory.

18-19: X2 and X1: Input and output of internal oscillator. Quartz crystal

controlling the frequency commonly connects to these pins. Capacitances within

the oscillator mechanism (see the image) are not critical and are normally about

30pF. Instead of a quartz crystal, miniature ceramic resonators can be used for

dictating the pace. In that case, manufacturers recommend using somewhat higher

capacitances (about 47 puff). New Mucus works at frequencies from 0Hz to

50MHz+.The basic crystal circuit is as shown in the figure 2.2.4.b.

FIG: 2.2.4.b:Crystal circuit

20: GND : Ground

21-28: Port 2: if external memory is not present, pins of Port 2 act as universal

input/output. If external memory is present, this is the location of the higher

address byte, i.e. addresses A8 A15. It is important to note that in cases when not



12/33

all the 8 bits are used for addressing the memory (i.e. memory is smaller than

64kB), the rest of the unused bits are not available as input/output.

PIN29: PSEN: MCU activates this bit (brings to low state) upon each reading of

byte (instruction) from program memory. If external ROM is used for storing theprogram, PSEN is directly connected to its control pins.

PIN30: of the external memory, MCU sends the lower byte of the address register

(addresses A0 A7) to port P0 and activates the output ALE. External register

(74HCT373 or 74HCT375 circuits are common), memorizes the state of port P0

upon receiving a signal from ALE pin, and uses it as part of the address for

memory chip. During the second part of the mechanical MCU cycle, signal on

ALE is off, and port P0 is used as Data Bus. In this way, by adding only one cheap

integrated circuit, data from port can be multiplexed and the port simultaneously

used for transferring both addresses and data.

PIN31: EA/VPP: Bringing this pin to the logical state zero (mass) designates the

ports P2 and P3 for transferring addresses regardless of the presence of the internal

memory. This means that even if there is a program loaded in the MCU it will not

be executed, but the one from the external ROM will be used instead. Conversely,

bringing the pin to the high logical state causes the controller to use both

memories, first the internal, and then the external (if present).

32-39: Port 0: Similar to Port 2, pins of Port 0 can be used as universal

input/output, if external memory is not used. If external memory is used, P0

behaves as address output (A0 A7) when ALE pin is at high logical level, or as

data output (Data Bus) when ALE pin is at low logical level.

40: VCC: Power +5V

Input Output (I/O) Ports :

Every MCU from 8051 families has 4 I/O ports of 8 bits each. This

provides the user with 32 I/O lines for connecting MCU to the environs. Unlike the case

with other controllers, there is no specific SFR register for designating pins as input or

output. Instead, the port itself is in charge: 0=output, 1=input. If particular pin on the case

is needed as output, the appropriate bit of I/O port should be cleared. This will generate

0V on the specified controller pin. Similarly, if particular pin on the case is needed as



13/33

input, the appropriate bit of I/O port should be set. This will designate the pin as input,

generating +5V as a side effect (as with every TTL input).

Port 0

Port 0 has two-fold role: if external memory is used, it contains the lower address

byte (addresses A0-A7); otherwise all bits of the port are either input or output. Another

feature of this port comes to play when it has been designated as output. Unlike other

ports, Port 0 lacks the "pull up" resistor (resistor with +5V on one end). This seemingly

insignificant change has the following consequences:

When designated as input, pin of Port 0 acts as high impedance offering the

infinite input resistance with no "inner" voltage.

When designated as output, pin acts as "open drain". Clearing a port bit grounds

the appropriate pin on the case (0V). Setting a port bit makes the pin act as high

impedance.

Therefore, to get positive logic (5V) at output, external "pull up" resistor needs to

be added for connecting the pin to the positive pole.

Therefore, to get one (5V) on the output, external "pull up" resistor needs to be

added for connecting the pin to the positive pole.

Port 1

This is "true" I/O port, devoid of dual function characteristic for Port 0. Having the

"pull up" resistor, Port 1 is fully compatible with TTL circuits.

Port 2

When using external memory, this port contains the higher address byte (addresses

A8A15), similar to Port 0. Otherwise, it can be used as universal I/O port.

Port 3

Beside its role as universal I/O port, each pin of Port 3 has an alternate function. In

order to use one of these functions, the pin in question has to be designated as input, i.e.



14/33

the appropriate bit of register P3 needs to be set. From a hardware standpoint, Port 3 is

similar to Port 0.

As can be seen from the individual descriptions of the ports, they all share highly

similar structure. However, you need to consider which task should be assigned to which

port. For example: if utilizing port as output with high level (5V), avoid using Port 0, as its

pins cannot produce high logical level without an additional resistor connected to +5V. If

using other port to a same end, bear in mind that built-in resistors have relatively high

values, producing the currents limited to few hundreds of amperes as pin output.

Memory Under The Magnifier:

During the runtime, micro controller uses two different types of memory: one for

holding the program being executed (ROM memory), and the other for temporary storage

of data and auxiliary variables (RAM memory). Depending on the particular model from

8051 family, this is usually few kilobytes of ROM and 128/256 bytes of RAM. This

amount is built-in and is sufficient for common tasks performed "independently" by the

MCU. However, 8051 can address up to 64KB of external memory. These can be separate

memory blocks, (separate RAM chip and ROM chip) totaling 128KB of memory on

MCU, which is a real programming goody.

ROM memory:

First models from 8051 family lacked the internal program memory, but it could be

added externally in a form of a separate chip. This Mucus can be recognized by their

mark, which begins with 803 (e.g. 8031 or 8032). New models have built-in ROM,

although there are substantial variations. With some models internal memory cannot be

programmed directly by the user. Instead, the user needs to precede the program to the

manufacturer, so that the MCU can be programmed (masked) appropriately in the process

of fabrication. Obviously, this option is cost-effective only for large series. Fortunately,

there are MCU models ideal for experimentation and small specialized series. Many

manufacturers deliver controllers that can be programmed directly by the user. These

come in a ceramic case with an opening (EPROM version) or in a plastic case without an

opening (EEPROM version). This book deals with one of the latter models that can be

programmed via simple programmer, even if the chip has already been mounted to the

designated device.



15/33

RAM memory:

As previously stated, RAM is used for storing temporary data and auxiliary results

generated during the runtime. Apart from that, RAM comprises a number of registers:

hardware counters and timers, I/O ports, buffer for serial connection, etc. With olderversions, RAM spanned 256 locations, while new models feature additional 128 registers.

First 256 memory locations form the basis of RAM (addresses 0 Fifth) of every 8051

MCU. Locations that are available to the user span addresses from 0 to 7Fh, i.e. first 128

registers, and this part of RAM is split into several blocks as can be seen in the image

below 3.2.1b.

Fig:3.2.1b RAM Memory in 8051 microcontroller

First block comprises 4 "banks" of 8 registers each, marked as R0 - R7. To address

these, the parent bank has to be selected.

Second memory block (range 20h 2Fh) is bit-addressable, meaning that every

belonging bit has its own address (0 to 7Fh). Since the block comprises 16 of these



16/33

registers, there is a total of 128 addressable bits. (Bit 0 of byte 20h has bit address

0, while bit 7 of byte 2Fh has bit address 7Fh).

Third is the group of available registers at addresses 2Fh 7Fh (total of 80

locations) without special features or a preset purpose.

Extra Memory Block:

To satisfy the programmers' ever-increasing demands for RAM, latest 8051 models

were added an extra memory block of 128 locations. But it is not all that simple... The

problem lies in the fact that the electronics, which addresses RAM, employs 1 byte (8

bits), reaching only the first 256 locations. Therefore, a little trick had to be applied in

order to keep the existing 8-bit architecture for the sake of compatibility with older

models. The idea is to make the additional

Memory Expanding:

In case the built-in amount of memory (either RAM or ROM) is not sufficient for

your needs, there is always an option of adding two external 64KB memory chips. When

added, they are addressed and accessed via I/O ports P2 and P3. From user's point of view

it's all very simple, because if properly connected most of the job is carried out

automatically by MCU.



17/33

8051 MCU has two separate read signals, RD# (P3.7) and PSEN#. The first one is

active when reading byte from the external data memory (RAM), and the second one is

active when reading byte from the external program memory (ROM). Both signals are

active on low logical level. The following image shows a typical scheme for such

expansion using separate chips for RAM and ROM, known as Harvard architecture.

Memory simultaneously (only one memory chip is used) . This approach is known

as Von Neumann architecture. To be able to read the same block using RD# or PSEN#,

these two signals were combined via logical AND. In this way, output of AND circuit is

low if any of the two inputs is low.

Using the Harvard architecture effectively doubles MCU memory, but that's notthe only advantage offered by the method. Keeping the program code separated from the

data makes the controller more reliable since there is no writing to the program memory

SFR Registers (Special Function Registers):

SFR registers can be seen as a sort of control panel for managing and monitoring

the micro controller. Every register and each of the belonging bits has its name, specified

address in RAM and strictly defined role (e.g. controlling the timer, interrupt, serial

connection, etc). Although there are 128 available memory slots for allocating SFR

registers, the basic core shared by 8051 Mucus has but 22 registers. The rest has been left

open intentionally to allow future upgrades while retaining the compatibility with earlier

models. This fact makes possible to use programs developed for obsolete models long ago.



18/33


19/33

Features

1. 433.92 MHz Frequency

2. Low Cost

3. 1.5-12V operation

4. 11mA current consumption at 3V

5. Small size

6. 4 dBm output power at 3V

Applications1. Remote Keyless Entry (RKE)

2. Remote Lighting Controls

3. On-Site Paging

4. Asset Tracking

5. Wireless Alarm and Security Systems

6. Long Range RFID

7. Automated Resource Management

Pin Description



20/33

ANT:

50 ohm antenna output. The antenna port impedance affects output power and

harmonic emissions. An L-C low-pass filter may be needed to sufficiently filter harmonic

emissions. Antenna can be single core wire of approximately 17cm length or PCB trace

antenna.

VCC:

Operating voltage for the transmitter. VCC should be by passed with a .01uF

ceramic capacitor and filtered with a 4.7uF tantalum capacitor. Noise on the power supply

will degrade transmitter noise performance.

DATA:

Digital data input. This input is CMOS compatible and should be driven with

CMOS level inputs.

GND:

Transmitter ground. Connect to ground plane.



21/33

Operation

Theory

OOK (On Off Keying) modulation is a binary form of amplitude modulation.

When a logical 0 (data line low) is being sent, the transmitter is off, fully suppressing the

carrier. In this state, the transmitter current is very low, less than 1mA. When a logical 1 is

being sent, the carrier is fully on. In this state, the module current consumption is at its

highest, about 11mA with a 3V power supply.

OOK is the modulation method of choice for remote control applications where

power consumption and cost are the primary factors. Because OOK transmitters draw no

power when they transmit a 0, they exhibit significantly better power consumption than

FSK transmitters.

OOK data rate is limited by the start-up time of the oscillator. High-Q oscillators

which have very stable center frequencies take longer to start-up than low-Q oscillators.

The start-up time of the oscillator determines the maximum data rate that the transmitter

can send.

STR 433Mhz RF receiver

The STR-433 is ideal for short-range remote control applications where cost is a

primary concern. The receiver module requires no external RF components except for the

antenna. The super-regenerative design exhibits exceptional sensitivity at a very low cost.



22/33

Features

1. Low Cost2. 5V operation

3. 3.5mA current drain

4. No External Parts are required

5. Receiver Frequency: 433.92 MHZ

6. Typical sensitivity: -105dBm

7. IF Frequency: 1MHz

Applications

1. Car security system

2. Sensor reporting

3. Automation system

4. Remote Keyless Entry (RKE)

5. Remote Lighting Controls

6. On-Site Paging

7. Asset Tracking

8. Wireless Alarm and Security Systems

9. Long Range RFID

10. Automated Resource Management



23/33

PIN SIGNALS:

ANT Antenna input.

GND Receiver Ground. Connect to ground plane.

VCC(5V) VCC pins are electrically connected and provide operating voltage for the

receiver. VCC can be applied to either or both. VCC should be bypassed with a .1F

ceramic capacitor. Noise on the power supply will degrade receiver sensitivity.

DATA Digital data output: This output is capable of driving one TTL or CMOS load. It

is a CMOS compatible output.

Operation

Super-Regenerative AM Detection

The STR-433 uses a super-regenerative AM detector to demodulate the incomingAM carrier. A super regenerative detector is a gain stage with positive feedback greater

than unity so that it oscillates. An RC-time constant is included in the gain stage so that

when the gain stage oscillates, the gain will be lowered over time proportional to the RC

time constant until the oscillation eventually dies. When the oscillation dies, the current

draw of the gain stage decreases, charging the RC circuit, increasing the gain, and

ultimately the oscillation starts again. In this way, the oscillation of the gain stage is turned

on and off at a rate set by the RC time constant. This rate is chosen to be super-audible but

much lower than the main oscillation rate. Detection is accomplished by measuring the

emitter current of the gain stage. Any RF input signal at the frequency of the main

oscillation will aid the main oscillation in restarting. If the amplitude of the RF input

increases, the main oscillation will stay on for a longer period of time, and the emitter

current will be higher. Therefore, we can detect the original base-band signal by simply

low-pass filtering the emitter current.



24/33

The average emitter current is not very linear as a function of the RF input level. It

exhibits a 1/ln response because of the exponentially rising nature of oscillator start-up.

The steep slope of a logarithm near zero results in high sensitivity to small input signals.

Data Slicer

The data slicer converts the base-band analog signal from the super-regenerative

detector to a CMOS/TTL compatible output. Because the data slicer is AC coupled to the

audio output, there is a minimum data rate. AC coupling also limits the minimum and

maximum pulse width. Typically, data is encoded on the transmit side using pulse-width

modulation (PWM) or non-return-to-zero (NRZ).The most common source for NRZ data

is from a UART embedded in a micro-controller. Applications that use NRZ data

encoding typically involve microcontrollers. The most common source for PWM data is

from a remote control IC such as the HC-12E from Holtek or ST14 CODEC .Data is sent

as a constant rate square-wave. The duty cycle of that square wave will generally be either

33% (a zero) or 66% (a one). The data slicer on the STR-433 is optimized for use with

PWM encoded data, though it will work with NRZ data if certain encoding rules are

followed.

Power Supply

The STR-433 is designed to operate from a 5V power supply. It is crucial that this

power supply be very quiet. The power supply should be bypassed using a 0.1uF low-ESR

ceramic capacitor and a 4.7uF tantalum capacitor. These capacitors should be placed as

close to the power pins as possible. The STR- 433 is designed for continuous duty

operation. From the time power is applied, it can take up to 750mSec for the data output to

become valid.

Antenna Input

It will support most antenna types, including printed antennas integrated directly

onto the PCB and simple single core wire of about 17cm. The performance of the different

antennas varies. Any time a trace is longer than 1/8th the wavelength of the frequency it is

carrying, it should be a 50 ohm micro strip.



25/33

2.1.2 KEYPAD

keyboard is organized in a matrix of rows and columns

the key press is scanned and identified by microcontroller

Figure . Matrix Keyboard Connection to Ports

A scan program and its flow chart are shown as follows



26/33



27/33

2.1.3 LCD (Liquid Crystal Diode):

Introduction:

Frequently, an 8051 program must interact with the outside world using input and

output devices that communicate directly with a human being. One of the most common

devices attached to an 8051 is an LCD display. Some of the most common LCDs

connected to the 8051 are 16x2 and 20x2 displays. This means 16 characters per line by 2

lines and 20 characters per line by 2 lines, respectively. Now a day, LCD is finding

widespread use in place of LEDs. The ability to display numbers, characters. This is in

contrast to LEDs.

LCD interfacing with 8051 micro controller:

LCD pin description:

The LCD discussed in this section has 14 pins. The functions of each pin are given

in table.



28/33

Vcc, Vss, and Vee:

While Vcc and Vss provide +5v and ground, respectively. Vee is used for

controlling LCD contrast.

RS, register select:

There are two very important registers inside the LCD. The RS pin is used for their

selection as follows. If RS=0, the instruction command code register is selected, allowing

the user to send a command such as clear display, cursor at home, etc. if RS=1 the data

register is selected, allowing the user to send data to be displayed on the LCD.

R/W, read/write:

R/W input allows the user to write information to the LCD or read information

from it. R/W=1 when reading; R/W=1 when writing.

E, enable:

The LCD to latch information present to its data pins uses the enable pin. When

data is supplied to data pins, a high-to-low pulse must be applied to this pin.

D0-D7:

The 8-bit data pins, D0-D7, are used to send information to the LCD or read the

contests of the LCDs internal registers. To display the letters and numbers, we send

ASCII codes for the letters A-Z, a-z and numbers 0-9 to these pins while making RS=1.



29/33

There are also codes that can be sent to the LCD to clear the display or force the cursor to

the home position or blink the cursor. These commands are given below table.

We also use RS=0 to check the busy flag bit to see if the LCD is ready to receive

information. The busy flag is D7 and can be read when R/W =1, RS=0, when D7=1, the

LCD is busy taking care of the internal operations and will not accept any new

information.



30/33

CHAPTER 4

SOFTWARE TOOLS

4.1 KEIL IDE

Keil development tools for the 8051 Microcontroller Architecture support every

level of software developer from the professional applications engineer to the student just

learning about embedded software development.

The industry-standard Keil C Compilers, Macro Assemblers, Debuggers, Real-

time Kernels, Single-board Computers, and Emulators support all 8051 derivatives and

help you get your projects completed on schedule.

6.1.1

The Vision IDE from Keil combines project management, make facilities, source

code editing, program debugging, and complete simulation in one powerful environment.

The Vision development platform is easy-to-use and it helps you quickly create

embedded programs that work. The Vision editor and debugger are integrated in a single

application that provides a seamless embedded project development environment.

4.1.2 DEVELOPMENT CYCLES

The Keil 8051 Development Tools are designed to solve the complex problems

facing embedded software developers.

1. When starting a new project, simply select the microcontroller you use from the

Device Database and the Vision IDE sets all compiler, assembler, linker, and

memory options for you.

2. Numerous example programs are included to help you get started with the most

popular embedded 8051 devices.

3. The Keil Vision Debugger accurately simulates on-chip peripherals (IC, CAN,UART, SPI, Interrupts, I/O Ports, A/D Converter, D/A Converter, and PWM

Modules) of your 8051 device. Simulation helps you understand hardware

configurations and avoids time wasted on setup problems. Additionally, with

simulation, you can write and test applications before target hardware is available.

4. When you are ready to begin testing your software application with target

hardware, use the MON51, MON390, MONADI, or FlashMON51 Target



31/33

Monitors, the ISD51 In-System Debugger, or the ULINK USB-JTAG Adapter to

download and test program code on your target system.

Third-Party Utilities

extend the functions

and capabilities of Vision.

Keil PK51 is a complete software development environment for classic and extended 8051

microcontrollers. Like all Keil tools, it is easy to learn and use.

RTX Real-Time Kernels

enables the development of

real-time software



32/33

PROJECT MANAGER

Getting Started

The Vision IDE is the easiest way for most developers to create embedded applications

using the Keil development tools. To launch Vision, click on the icon on your desktop or

select Keil Vision3 from the Start Menu.

Vision includes a number of example projects you may use to get familiar with the tools

and capabilities that are available.

TARGET DEBUGGER

The Vision Debugger from Keil supports simulation using only your PC or laptop, and

debugging using your target system and a debugger interface. Vision includes traditional

features like simple and complex breakpoints, watch windows, and execution control as

well as sophisticated features like trace capture, execution profiler, code coverage, and

logic analyzer.



33/33

BIBLIOGRAPHY

Microcontrollers Architecture, Programming, Interfacing and

System Design

by RajKamal

Rf Based Advertisment System

Documents

Transcript of Rf Based Advertisment System